Glacial Erratics

[otseng]

This thread is an offshoot of Drumlins, Ribbed Moraines, and Giant Ripples. Though these are all related, I'd like to narrow down on erratics in this thread.

A glacial erratic is a piece of rock carried by glacial ice some distance from the rock outcrop from which it came. Erratics can range in size from pebbles to massive pieces such as the Okotoks (16,500 tons) and Airdrie erratics found in Alberta, Canada. They can be found miles away from their original location.

http://en.wikipedia.org/wiki/Glacial_erratic

For debate:
How did these rocks get there?

[WelshBoy]

Haha, now now, that wasn't my inference as you well know !

A little rain over a VERY long time is what I meant, not a lot of rain over a SHORT time. I'm merely hypothesising, I don't have the geological expertise to answer my own question...

[otseng]

If it is true that erratics are a result of boulders falling off of a mountain and being carried by glaciers, I think there are several things that we should see.

1. There should be little to no erosional evidence on the erratics.

2. Should be able to identify possible mountains that the rock could have come from. Generally it should be in a northern direction of where the rock was found.

3. Should be able to match the erratic composition with the rocks at the mountain.

4. There should be more erratics located south of mountain ranges. And little to none where there are no mountains.

5. Erratics should be found in groups since rock slides generally produce many boulders.

And from what I tell, erratics generally fail to meet these conditions.